Design and analysis of novel D–π–A configuration dyes for dye-sensitized solar cells: a density functional theory study

This study explores the electronic, optical, and electrochemical properties of novel D–π–A organic dyes with different π-bridges using DFT and TD-DFT calculations, emphasizing their potential as efficient light harvesters. Geometric analysis shows that the dyes’ bond lengths and dihedral angles support intramolecular charge transfer, light absorption, and stability. The π-bridge improves electronic coupling, promoting conjugation and electron mobility. Frontier molecular orbital analysis reveals HOMO and LUMO levels aligned with TiO₂ conduction band and the electrolyte's redox potential, ensuring efficient electron injection and dye regeneration. The dyes’ energy gaps (2.1151–2.5426 eV) enable effective visible-light absorption. Molecular orbital distribution supports charge separation for efficient donor-to-acceptor electron transfer. Global reactivity parameters indicate high stability and enhanced charge transfer capabilities. Molecular electrostatic potential and reduced density gradient analyses highlight charge distribution and non-covalent interactions that improve stability and electronic properties. UV–Vis spectra (543.021–624.762 nm) reveal enhanced light-harvesting efficiency via n → π* transitions enabled by the π-bridge. Electrochemical parameters, including oxidation potential and free energy changes, confirm their suitability for DSSCs. These dyes demonstrate significant potential for renewable energy applications, particularly in DSSCs.